1. Field of the Invention
The present invention relates to a pump for pumping fluids and other flowable materials, and especially but not exclusively to a gear pump for use in a dispensing apparatus. More particularly, the gear pump may be used in a machine for making paints and the like consisting of a selection of colorants dispensed from containers through gear pumps.
2. Description of the Related Art
Due to environmental requirements and other constrants, colorants for paint contain less lubricating components and are more abrasive than some other fluids. This has set high demands on gear pumps, and one of the ways of meeting the high demands is using ceramic parts, especially for the gears. The ceramic components are very reliable and wear resistant. Moving parts hardly need any lubrication between sliding surfaces thereof.
An example of a gear pump having ceramic gears is shown in U.S. Pat. No. 5,785,510. Another gear pump having ceramic gears is disclosed in EP-A-0 866 224. A pump having ceramic seal parts is disclosed in U.S. Pat. No. 4,911,609.
It is an object of the present invention to provide an improved pump showing excellent properties, especially regarding reliability and sealing of the housing.
The object of the invention is obtained in a gear pump comprising:
a housing having an inlet and an outlet,
at least first and second gears, each having gear teeth, said gear teeth of the first gear being in engagement with the gear teeth of the second gear,
at least the first gear being a ceramic rotor gear which is journaled within the housing and is connected to a drive shaft for driving it in order to move it relative to the second gear, such as to pump a fluid from the inlet to the outlet of the housing,
wherein the housing includes an opening for the passage of the drive shaft and a seal surrounding the opening, said seal comprising a first seal part rotating with the first gear, and a second seal part forming a part of the housing or carried thereby, said first and second seal parts having facing sealing surfaces, and wherein at least one of said first and second seal parts being made of ceramic material and the sealing surfaces being loaded towards each other by a biasing member acting parallel to the drive shaft.
The gears are preferably made of ceramic material. In a preferred embodiment, the housing includes an inner housing of ceramic material and an outer cover of injection molded plastics material forming the single piece mold of the housing.
According to another aspect of the invention the fluid pump comprises:
a housing having a wall and an inlet and outlet being formed in the housing wall,
at least one rotatable ceramic pumping member which is journaled within the housing and includes a drive shaft for driving it in order to rotate it, such as to pump a fluid from the inlet to the outlet of the housing,
wherein the housing includes an opening in its wall for the passage of the drive shaft and a seal surrounding the opening, said seal comprising a first seal part rotating with the pumping member, and a second seal part forming part of the housing wall, said first and second seal parts having facing sealing surfaces, and wherein said first and second seal parts being made of ceramic material and being loaded towards each other by a biasing member parallel to the drive shaft.
In an embodiment, a gear pump comprises a housing having inlet and an outlet. The housing is lined with a sealing liner that defines a pump chamber. The sealing liner is preferably in the form of two parts but a unitary construction is possible. The pump also includes first and second gears disposed in the pump chamber. Each gear has teeth and the teeth of the first gear are in engagement with or enmeshed with the gear teeth of the second gear. At least the first gear is a ceramic rotor gear which is journaled within the pump housing. The first gear is connected to a drive shaft. The housing and sealing liner include openings for passage of the drive shaft. The seal surrounds the opening of the sealing liner and rotates with the first gear. The seal and the sealing liner have facing sealing surfaces and both the seal and sealing liner are fabricated from ceramic material and are loaded towards each other by a biasing member parallel to the drive shaft. Thus, the present invention utilizes a portion of the sealing liner, which defines the pump chamber, as a seal mechanism for sealing the pump chamber with the first and second gears disposed therein.
As a result of the invention, the housing has very good and reliable sealing properties since the ceramic seal parts do not need lubrication and are very resistant to wear. The structure of the seal can be simple and assembly is easy, in particular if the gears only have a single bearing journal on one side as thereby aligning problems are avoided. Especially when ceramic components are used, the gear pump is very durable and requires no maintenance.
The invention will hereafter be further explained with reference to the drawing showing an embodiment of the invention by way of example.